Conventional flip chip semiconductor light emitting diodes are generally used because of high current diffusion efficiency and optical extraction efficiency, and excellent thermal characteristics with a silicon sub mount (see FIG. 1).
However, the flip chip semiconductor light emitting diodes have problems such as loss of active layer area caused by mesa-etching and drop of reflector layer efficiency caused by metal pads formed with big size.
In addition, though vertical type chip structure, which is recently developed by removing a sapphire substrate, has advantages of brightness enhancement due to increased light emitting area as compared with a lateral type light emitting diode, there are problems such as degradation of electrical characteristics and reliability due to a problem of ohmic contact formed between a N contact pad and a n type semiconductor layer at the area where the substrate is removed.
In addition, conventional nitride semiconductor light emitting diodes generally have a sapphire substrate, and on that, a layer sequence of a buffer layer, a n type nitride semiconductor layer, an active layer of multiple quantum well (MQW), a p type nitride semiconductor are formed in sequence. The p type nitride semiconductor layer and the active layer have the structure that a part of their area is eliminated with processes such as etching, thus exposing a part of the upper side of the n type nitride semiconductor. An n type electrode is formed on the exposed n type nitride semiconductor layer, and a p type bonding electrode is formed after a transparent electrode is formed to make ohmic contact on the p type nitride semiconductor layer.
A light emitting diode made with a conventional manufacturing process may be bonded on sub mount substrate made of silicon or ceramic as a package type for practical use or mounted on other types of packages.
Processes such as die bonding to bond the light emitting diode with these package materials and wire bonding for injecting electrons and holes are essential to a conventional light emitting diode manufacturing method.
FIG. 10 shows a sectional diagram of a light emitting diode stacked in the conventional light emitting diode manufacturing process, and the picture of electrons and holes movement.
Referring to FIG. 10, on a sapphire substrate 1100, an n type nitride semiconductor layer 1101, an active layer 1102 of multiple quantum well, a p type nitride semiconductor 1103 are formed in sequence. A p type electrode 1104 is located on the p type nitride semiconductor layer 1103, and an n type electrode is located on an exposed area, formed after etching, of the n type nitride semiconductor layer 1101.
The p type electrode and the n type electrode has a structure for being connected to PCB or other packages with wire 1106.
Generally, a buffer layer working as a buffer may be included between a substrate and a semiconductor layer in a conventional structure.
Referring to FIG. 10, electrons and holes from different semiconductor areas come together in the active layer, thus emitting light and generating it outside.
Due to the module structure made according to a conventional light emitting diode manufacturing method, the total thickness of a package gets thicker to cause problems of low optical extraction efficiency and performance, and also problems of yield and productivity related to complex processing.
Changing these package types may means a cost burden such as establishing a new production line. Therefore, it has been required to suggest improved structure of a light emitting diode module while maintaining current package types and processes.